Based on a nonrepresentative world survey, active and intelligent packaging sizzles! The “world survey” covers two conferences in the United States, one in the Netherlands, one organized by the United Kingdom’s Campden & Chorleywood Food Research Association, and one in Australia; one IFT Food Packaging Division symposium at IFT’s 2001 Annual Meeting, featuring an array of stars from around the world; two multiclient study proposals, one prepared by an expert in the field; and a book written by me and two associates, due for publication soon.
With so much activity in active packaging, some semblance of direction can be provided by reviewing one of the recent events in the UK, and dividing the column into the two separate parts—active packaging and intelligent packaging—as the conference organizer attempted to do.
Active packaging senses environmental changes and responds by changing its properties. Intelligent packaging, relatively new on the scene, measures a component and signals the result. The former is typified by oxygen scavengers, antimicrobials, and controllers of odor, moisture, and carbon dioxide. The latter includes electronic locators, anti-theft and anti-counterfeiting devices, time–temperature integrators, and the newest pathway of our intelligence, the signaling of the presence of spoilage and/or pathogenic microorganisms in the food.
The reasons for the increased interest in active packaging stems from the known limitations of barrier packaging in controlling the internal environments of food (and other) packages. Barrier structures can only keep out (or in) elements that are already present. To enhance the value of the packaging to the contents, active agents can be incorporated to overtly act when something is amiss. For example, the oxygen sensitivity of moist pasta has been documented. Removal of oxygen, both residual and that entering through the plastic package walls or seals, may be achieved by affixing an oxygen-scavenger sachet to the interior of the package wall to extend the quality of the pasta and suppress aerobic microorganisms.
The September 2000 Campden & Chorleywood Food Research Association’s International Conference on Active and Intelligent Packaging assembled the leaders in technology and marketing in both categories to discuss issues and ramifications. Most of the participants had a specific agenda, so no single consensus was reached. The emerging discipline is so broad that the sole unifying element was that the subjects were active packaging—which did not include many of the more intriguing new technologies. Furthermore, most of the participants were from European governments or university research organizations, with their interests in information, while others clearly were trying to sell their particular product.
· Overview. Joost Vermuë of the Netherlands’ TNO offered a summary overview of active packaging whose purposes are to extend shelf life, improve safety, and improve sensory properties. Active packaging falls into three categories: scavenging, releasing, and “other.” Scavengers include those for oxygen, ethylene, moisture, and taint. Oxygen-scavenging systems include sachets, labels, closures, and polymers incorporated directly into flexible package materials. Oxygen scavengers may deliver protection against aerobic microbiological growth, lipid oxidation, discoloration, flavor loss, and loss of nutritive elements.
Oxygen scavenging must account for residual oxygen in the product and headspace, leakage through openings, permeation, and inadequate evacuation during processing and packaging. Taint scavengers remove undesirable odors such as those arising from fish spoilage or lipid oxidation. However, taint scavengers can create unsafe situations in removing signals that the product is no longer safe for consumption. Removing the signal may give consumers an unrealistic feeling of safety. Moisture absorbers can help to control humidity for both low-moisture products such as cookies and high-moisture products such as meat, produce, and fish. Active release concepts include release of antimicrobials, such as silver salts, alcohol, sulfur dioxide, and bacteriocins, and antioxidants, such as BHA, BHT, and tocopherols.
· Regulatory Aspects. Dario Dainelli of Cryovac Sealed Air discussed some of the European regulatory aspects of active packaging. No specific European Community regulations govern active packaging, but some active packaging has the potential to generate compounds capable of migrating into the contained food. For example, biocidal films are, by definition, not inert and so must meet migration limitations.
Nico de Kruijf, also of TNO, described EC Fair “Actipak,” the European initiative to objectively evaluate active packaging concepts for their safety and efficacy. Among the objectives of the industry–university–government consortium is to determine what, if any, regulation might be required to ensure the safety of active packaging and to promote the competitive position of the European industry.
· Oxygen Scavengers. Mitsubishi Gas Chemical’s Yoshihisa Sakakibara from Japan provided a picture of his company’s well-known oxygen scavengers and of the new products in the category being offered. Mitsubishi Gas Chemical and its Ageless® scavenger are regarded as the pioneers in ferrous-based oxygen-scavenger sachets. Unlike food additives, oxygen absorbers can help to preserve foods against oxygen-driven deteriorations without product alteration. With the sachet scavenger, the oxygen concentration within the package may be reduced to below 0.01%, well below what can be achieved with vacuum, gas flushing, and gas barrier together. Among the Japanese products that contain oxygen scavenging sachets are confectionery, dried seafood snacks, processed meat, rice cake, pasta, pizza crust, nuts, cheese, and dried vegetables.
Mitsubishi Gas Chemical is now offering the ferrous iron chemistry in flat label form in which the active iron powder is contained in the plastic. The product, perhaps using a different chemistry, is also available in card form that can be formed to any shape and inserted or affixed to the package interior.
Australia’s eminent oxygen scavenger expert, Michael Rooney, described the oxygen-scavenging films of Food Science Australia (formerly CSIRO). Rooney pointed out that more than 60 worldwide patents have been issued on oxygen-scavenging sachets and 50 on plastics. Most of the recent published work has been on incorporation of oxygen scavengers into plastics such as multilayer film and PET bottles. Zero2™ is the designation for a range of Australian oxygen scavenging plastic packaging materials in which the reactive components are activated by means of ultraviolet or related high-energy processes.
The plastics are inactive until activated and so can be subjected to conventional plastics converting processes to make films, sheet, adhesives, lacquers, closure liners, and can coatings. Test results with Zero2 materials in flexible laminations suggest that mold can be inhibited without carbon dioxide and that ham discoloration can be prevented even under visible light. Orange juice in EVOH/polyethylene barrier laminations containing the scavenger demonstrated zero oxygen within three days at 4°C and half the loss of vitamin C after one year, compared to conventional barrier packaging. Shelf life of wine in bag-in-box was increased by 33% using the oxygen scavenger, compared to conventional gas barrier.·
Ethylene Adsorbers. Liesbeth Jacxens of Belgium’s Ghent University provided the basis for the elimination of ethylene in postharvest plant environments, and suggested methods for its removal. Removal of ethylene from the plant environment can significantly retard postharvest catabolic activity in fresh produce, and complement modified-atmosphere preservation processes. Potassium permanganate reacts with ethylene to eventually produce carbon dioxide and water. KMNO4 can be adsorbed onto inorganic substrates for incorporation into gas-permeable sachets to permit reaction with ethylene, a not-uncommon commercial practice for fresh produce transport. Large-capacity sachets required for small packages are awkward for consumer-size packages. Among the alternatives have been incorporation of activated carbon impregnated with palladium catalyst and blending with plastic film.
Activated earths such as zeolites or clays imbedded in plastic film are employed in Japan to adsorb ethylene. Whether these materials actually remove ethylene from the internal package environment or greatly increase the ethylene transmission of the plastic remains a question. To date, results of the true effectiveness of minerals in package materials are in question despite their apparently widespread use in Asian countries.
· Antimicrobial Films. L. Vermieren, also from Ghent University, discussed the range and realities of antimicrobial films. The most widely publicized are silver salts on zeolite incorporated into plastic film and sheet. These structures, popular in Japan, require direct contact of the silver ion with the food surface and its microorganisms to act. The reaction is highly dependent on the nature of the substrate. The silver may preferentially react with the food itself or alter its activity as a result of pH or the presence of salt.
In another variation, the catalytic action of silver in the presence of light and/or water at polar surfaces results in a change of gaseous oxygen into active oxygen, which causes structural damage to microorganisms. This reaction might possibly be the production of hydrogen peroxide. Effectiveness of and mechanisms for silver salts as antimicrobials in package materials remain as subjects for research to confirm the claims and to determine how they function, if indeed they do demonstrate desirable results when objectively examined.
Food Science Australia is developing systems to release sulfur dioxide to control mold growth on contained fruit. Obviously, being a gas, sulfur dioxide can permeate the product, but it can bleach fruit and cause discomfort to sensitive individuals.
A number of Japanese organizations have commercialized the application of allylisothiocyanate as an antimicrobial in plastic films. This mustard-and-horseradish extract is an effective antimicrobial but may not be rendered odor free.
· Antibacterials. Microban International’s Bill Rubinstein described his company’s product line and its status around the world. Ciba Geigy’s diphenylether derivative triclosan is marketed under the trade name Irgasan® DP-300. It is claimed to be a safe and effective antibacterial capable of long-term delivery. Upon contact with bacteria, including many pathogens, the compound penetrates the cell wall, destroying its ability to function. Because triclosan does not react chemically, microorganisms do not build resistance. The compound continuously migrates to the surface of the structure in which it is incorporated and thus is replenished.
Triclosan is targeted not as a primary antimicrobial, as it would probably be in single-use food packages, but rather as an agent that protects “between cleaning.” Despite its apparent effectiveness, it is not a substitute for conventional antimicrobial operations because its action in package films for food has not been demonstrated.
Bernàrd Technologies’ Peter Gray discussed Microatmosphère™ systems which generate chlorine dioxide. Sodium chlorite is incorporated into plastic materials and converted into chlorine dioxide, a powerful oxidizer that is highly soluble in water. Within the plastic, water reacts with a hydrophobic phase component to produce an acid that migrates to a hydrophilic phase, converting ionomeric chlorite to chlorine dioxide. Chlorine dioxide is highly active against a broad spectrum of microorganisms, including pathogens and sporeformers, functioning at very low concentrations (down to 0.05–5 ppm). The end products of the reaction, chloride ions, are innocuous.
Chlorine dioxide has received regulatory acceptance as sanitizing agents in food plants, as washes for cut fruit and vegetables, and for flour bleaching. It is also accepted by the Environmental Protection Agency for water treatment. It has not, however, received regulatory acceptance as an antimicrobial in food packaging applications. Its principal commercial application for food “packaging” is to control the microorganisms in the drip trays beneath fresh produce displays in supermarkets.
The next generation of food packaging will undoubtedly incorporate those few elements of active packaging that we understand today. Subsequent generations will be more active than passive if we read the current situation.
But these findings from the world’s leading experts should be disturbing: we may be rushing too fast. We are pioneering, treading into unknown territories. Even as apparently simple an act as removing oxygen from internal package environments has become an exercise in balance to ensure that the contained residuals do not overwhelm the scavenger and that the reaction compounds are neither toxic nor otherwise damaging to the contents. The oxygen-removal system must be both demonstrably effective and economic.
Most of the materials used in antimicrobial packaging are surface active only, and most food has irregular surfaces. Those compounds proposed to date which are not toxic to humans are not broad spectrum and so are meaningful only as complements to conventional microbial control methods. Some of the technologies proposed touch on our goal of package materials that have prolonged microbicidal and/or microbistatic effect within the entire package environment.
It is evident that information is lacking, not because of withholding of information by suppliers, but because the research has not been performed. What a wonderful opportunity for university graduate students to lead us into the future by doing the work that will propel us into the inevitable world of active packaging!
More information on the Proceedings of the International Conference on Active and Intelligent Packaging is available from Campden and Chorleywood Food Research Association, Chipping Campden, Gloucestershire GL55 6lD, UK (www.campden.co.uk).
Food products utilizing edible films and method of making and packaging same. U.S. patent 6,165,521, filed 3/31/1999, issued 12/26/2000 to W.G. Mayfield, assigned to Arriba Corp. Describes application of an edible material thin film to at least one side of sticky or moist food products. The edible material may be sprayed or placed on the moist food product. The food product with the edible material on it may be used make sandwiches or stored without any additional protection, or the individually wrapped slices may be further wrapped in plastic films, boxed, and transported. The food may be used to make a sandwich by peeling the amorphous food from the container and applying it to a slice of bread.
Resealable spout for side-gusseted packages. U.S. patent 6,164,826, filed 10/9/1998, issued 12/26/2000 to G.L. Petkovsek, assigned to Reynolds Consumer Products Inc. Describes a package with a surrounding wall enclosing a containment region and a spout. The spout is movable between a retracted position and a protracted position and features a resealable closure mechanism secured to the spout.
Dual compartment stand-up pouch. U.S. patent 6,164,822, filed 2/10/2000, issued 12/26/2000 to J.S. Beer, assigned to Fres-co System USA, Inc. Describes a dispensing package formed of a flexible material, e.g., a plastic film or laminate, with two separate compartments for holding paste-like materials until they are to be dispensed together from the package. The package also includes an outlet in the form of a fitment having a removable cap coupled to the two compartments.
Preservation of exposed cut fresh fruit. U.S. patent 6,159,512, first filed 12/21/1995, issued 12/12/2000 to V.G. Reyes, assigned to Australian Food Industry Science Centre. Describes a package of exposed fresh fruit consisting of cut pieces of fruit, a packaging material, and an edible gel. The packaging material encloses the fruit and allows transmission of oxygen and carbon dioxide to maintain an atmosphere about the fruit of at least 2% oxygen. The edible gel coats the exposed surfaces of the fruit and includes an antioxidant to retard browning and sufficient acidic constituents to establish and maintain a pH below 3 on the exposed surfaces of the fruit.
Method and a package for extending the shelf life of a food. U.S. patent 6,153,241, first filed 7/3/1995, issued 11/ 28/2000 to C.G. Beckeman, assigned to Tetra Laval Holdings & Finance S.A. Describes a method of achieving extended shelf life for a pumpable food that includes enclosing the food in a container of flexible or foldably formable material and treating the food in the container with heat in a treatment chamber, preferably an autoclave.
Boil-in-bag package. U.S. patent 6,153,232, filed 2/11/1999, issued 11/28/2000 to S. Holten, assigned to Uncle Ben’s, Inc. Describes an elongated rectangular-shaped boil-in-bag package for the storage and cooking of food items, such as rice. The bag has a closed top end and an open bottom end. A handle at the top end has an opening for receiving a lifting utensil. A sealing/release mechanism on the handle is configured to close the open bottom end of the bag to form a U-shaped package that allows fluid to flow between the inside walls of the U-shaped package. The sealing/release mechanism allows for the release of the open bottom end from the handle section without contacting the elongated bag section.
by AARON L. BRODY